p2 forces between objects when two objects push or pull on each other, they exert equal and opposite...

Forces between objects

When two objects push or pull on each other, they exert equal and opposite forces on one another e.g. you are

all pushing down on the floor, but the floor is also pushing up on you….if it didn’t you’d fall straight

through the floor!

LO: calculate the forces acting on an object

Resultant force

If you have multiple forces acting on an object, you can replace them with one single force that has the effect of all the other forces combined together. This single force

is called the resultant force


Calculating the resultant

A rocket produces a thrust of 2000N. It has a weight of 1000N. What is the resultant force acting on the rocket?



A rocket producing a resultant force of 1000N hits a wall, causing it to come to a stop. What force does the wall exert on the rocket and the rocket exert on the wall. Explain the reasoning for your answer.



A car of weight 5000N produces a driving force of 2000N. It experiences friction force from the ground of 500N and air resistance of 300N. What are the horizontal and vertical resultant forces acting on the car?


Rules for calculating the resultant

1. Forces that act in the same direction can be added together

2. Forces that act opposite to each other must be taken away

3. Forces that act vertically and horizontally CAN NOT be added and taken away from each other and MUST be considered separately.


Effects of forces 1LO: calculate the forces acting on an object

What is the resultant force on this book?

What would happen if the force was not zero?

• The resultant force on a stationary (not moving) object is zero!

• If a resultant force is applied to an object, it will accelerate in the direction of the force

Effects of forces 2LO: calculate the forces acting on an object

An arrow is fired from abow. What are the forcesacting on the arrow as it flies towards its target?

• If an object is moving with constant speed, the resultant force on it is zero

• If a resultant force is applied to a moving object, it will accelerate in the direction of the force

Calculating forces

• F = force (N)• m = mass (kg)• a = acceleration (m/s2)


F = m x a

m x a

F

Example 1A car of mass 400kg is accelerating at 5m/s2. What is the driving force produced by the engine?


Example 2A novice skier is being pulled along a horizontal section of a nursery slope. Given that her acceleration of 1.3m/s2 is provided by a force of 70N, calculate her mass.


Example 3A man pushes a car with a force of 200N along a straight horizontal road. He manages to accelerate the car by 0.1m/s². Find the mass of the car.


Graphs of motion

Graphs of motion are a visual representation of

the motion of a body

They can either show the change in displacement or

change in velocity of an object

LO: understand how to draw and interpret graphs of motion

Can you draw…

Mr R cycles into work. The journey takes him 15 minutes

(900s) and is a total distance of 3km (3000m). We will try to represent his journey using a

graph…


Can you draw…1. Mr R cycles to the first traffic light, a

distance of 500m away. It takes him 180 seconds to do this.

2. He waits at the traffic lights for 120 seconds while the light is red

3. When the light turns green, he cycles for 2000m without stopping. This takes him 5 minutes to do.

4. After 2000m, Mr R has to stop at another traffic light. He waits for 180 seconds.

5. Realising that he is about to be late, he sprints the last 500m in 120 seconds.


Mini-plenary1. Usain Bolt ran the 100m race in London 2012 in

approximately 9.6 seconds. He ran the first 20m in approximately 2.7 seconds after accelerating and running the final 80m in 6.9 seconds. It took him 20 metres to come to a stop, which he covered in 5 seconds. Draw a distance-time graph to show this journey.

2. Explain what a horizontal line on a distance-time graph represents

Extension:What do you think the steepness of a line on a distance-time graph represents?


Using distance-time graphs

• How steep the line is (the gradient) on a distance-time graph tells you the speed that an object is moving

• The steeper the line, the faster something is moving• Speed is measured in m/s


Calculating the gradient

Gradient =


Change in y

Change in x

Gradient = ∆y

∆x

Lets have a go at working out the speed that Mr C was travelling at during his journey to school!

One last definitionLO: understand how to draw and interpret graphs of motion

Two cars are travelling on a road in opposite directions. One is travelling

east at 20m/s and the other is travelling west at 20m/s. Their speeds

are exactly the same.However, their velocity’s are

different. What do you think their velocity’s are?

Velocity is the speed of an object in a given direction. Two objects can have the same speed, but very different

velocities

Can you draw…

Mr R has brought himself a slick new ride! He has also moved house and is now living in the

leafy suburbs. His journey takes him 1200 seconds, his top speed

is 50m/s and his lowest is -30m/s. Let’s plot his journey into school

on a velocity-time graph…


Can you draw…1. Mr R leaves his house. He is happily driving

along on country roads at a steady speed of 30m/s for two minutes…

2. D’oh! He’s forgotten his lunch. He turns round and drives back at 30m/s for two minutes. He is at home for 60s.

3. Back on the road, Mr R drives at 30m/s for 300s

4. Now on the motorway, Mr R is able to drive at 50m/s, which he does for 5mins

5. Coming off the motorway, he stops at a traffic light for 120s

6. Realising he is going to be late, he steadily increases his speed for the next 180 seconds from 0 to 50m/s. He arrives JUST on time!


Task1. What does a horizontal line on a velocity-time graph

represent?2. How do you know if an object has stopped by looking at

the velocity-time graph?3. How can you tell if an object is accelerating using a

velocity time graph?4. Draw the velocity-time graph for the following journey:

0-10s = 50m/s10-25s = 0m/s25-50s = 60m/s50-80s = acceleration to 80m/s


Acceleration

Acceleration is the change in speed of a body over a given amount of time


Acceleration

Acceleration can be calculated using the following equation:


Acceleration = Change in velocity

Time taken

Final velocity – initial velocity

Time takenAcceleration =

v - u

ta =

• a = acceleration (m/s2)• v = final velocity (m/s)• u = initial velocity (m/s)• t = time (s)

Example 1A car accelerates from a velocity of 10m/s to a velocity of 25m/s in 15 seconds. What is the acceleration of the car?


Example 2A runner starts at rest and accelerates to a top speed of 10m/s. If he does this in 2 seconds, what is his acceleration?


Example 3A train accelerates at 2m/s² for 30 seconds. If its initial velocity was 10m/s, calculate what the final velocity will be after 30 seconds.


Task1. What is the acceleration of a car that starts at rest and reaches

a top speed of 50m/s in 25 seconds?2. A plane starts at rest. It takes 8 seconds to take off and

accelerates at a constant rate of 10m/s². What is the final take-off velocity of the aircraft?

3. A runner starting at rest reaches a speed of 11m/s in 2.2 seconds during the drive phase of his 100m sprint. What is his acceleration during this phase? Assuming that his speed remains constant for the rest of the race, sketch the velocity-time graph for his journey

4. A car accelerates at 5m/s² for 12 seconds, reaching a final velocity of 80m/s. What was the car’s initial velocity before it started accelerating?


How are they linked?

The gradient of a velocity time graph represent the acceleration of an object!

Go back and calculate the acceleration of Mr C in the final part of his journey


Gradient = Change in y

Change in x

Gradient = ∆y

∆x

StreamliningLO: understand the factors that affect the stopping distance of a car

Most of the resistance forces that act on a car are due to air resistance.

Streamlining a car will increase the top speed, even if the engine is giving the same power output

Stopping distance

The stopping distance of a car is the minimum distance that a car can safely stop in

Stopping distance = thinking distance + braking distance

LO: understand the factors that affect the stopping distance of a car

Thinking distance

The thinking distance is the distance travelled by the vehicle in the time it takes for the driver to react


What factors will affectThe thinking distance

alcoholother drugs and some

medicines

tirednessdistractions, such as

mobile phones

speed

Stopping distance

The stopping distance is the distance travelled by the vehicle during the time the braking force acts


What factors will affectThe stopping distance

weather

condition of tyres/brakes

condition of roadspeed

Typical stopping distances

What effect would factors such as drugs, alcohol, tiredness, higher speed, adverse weather, poor road conditions or

worn out breaks have on these stopping distances?


Braking forceLO: understand the factors that affect the stopping distance of a car

Which of these would need the bigger force to stop if the stopping distance remained the same? Why?

QWC PracticeA local authority is worried about the number of road deaths

occurring in the area. They have imposed a ban on mobile phones while driving, imposed a speed limit of 30mph and installed speed cameras. Explain how the changes may lead to fewer people being

hit by cars.5-6 marks criteria:• Knowledge of accurate information appropriately contextualised• Detailed understanding, supported by relevant evidence and

examples• Answer is coherent and in an organised, logical sequence,

containing a wide range of appropriate or relevant specialist terms used accurately

• The answer shows almost faultless spelling, punctuation and grammar.


What is happening?LO: understand what is meant by terminal velocity

The graph below shows the velocity-time profile for a skydiver falling through the air. Discuss with the people on your pod what you think is happening and

why. Think about the forces that are involved at each stage

Moving in a fluidLO: understand what is meant by terminal velocity

Let’s think about what happens when an object moves through a

fluid by considering a skydiver

When the skydiver FIRST jumps out of the aircraft, gravity causes him

to accelerate.

The acceleration is a constant so the line on v-t graph will have an

unchanging steepness at the beginning


As the speed of the skydiver increases, the air resistance on him

increases.

The increased air resistance causes his acceleration to decrease. However, his velocity is still

increasing i.e. he’s speeding up slower than before, but he’s NOT

slowing down.


After a certain amount of time, the weight of the skydiver and the air resistance on the skydiver will be

balanced.

At this point, the skydiver will be moving at a constant velocity. This

is the MAXIMUM velocity it is possible for him to move with and

is known as the TERMINAL VELOCITY.


The process that we have just considered is relevant for ANY object

that is moving in a fluid e.g. a car driving along a road, a plane flying at 2000ft, a submarine underwater etc.

What factors will affectthe terminal velocity of

an object?


The factors that will increase/decrease the terminal velocity of an object are:• The driving force that the object

can generate• How streamlined the object is• The fluid that the object is

travelling through

Calculating weightLO: understand what is meant by terminal velocity

The weight of an object is the force that acts on an object due to gravity. It can be calculated using the following equation:

W = m x g

W = weight (Newtons)M = mass (kg)g = gravitational field strength (N/kg)

g has a value of 9.81 on earth

Changing shapeLO: understand the link between force and extension of an object

When a force is applied to an object, it may accelerate. However, a second effect that the force may cause is a change

in shape of the object

Stretching objectsLO: understand the link between force and extension of an object

When an object is stretched, it stores elastic potential energy.

Some objects are better at storing this energy than others. Which of the materials on your pod is better at storing elastic potential energy?

What happens when youstretch an object?

Material properties

Beyond a point, the material will start to show plastic behaviour.

A small increase in force will give a large increase in extension. The deformation will be irreversible (the material will not go back to the original shape when the force is taken away)

LO: understand the link between force and extension of an object

Beyond the proportional limit, the material shows plastic behaviour. The

extension is now much harder to predict

Real world application

Knowing how materials change shape under force is essential to most aspects of university.

The flexing of aircraft wings can dramatically change the lift generated. It also needs to be within limits to make sure the wings don’t break off!


Hooke’s Law

Hooke’s law states that:The extension of an object is directly proportional to the force that is applied to it provided that the limit of proportionality is not exceeded


Hooke’s Law

Hooke’s law can be written as:

F = k x e


• F = Force (N)• k = spring constant (N/m)• e = extension (m)

Task1. Calculate the spring constant for the spring that you did the

experiment with2. A spring is loaded with a force of 50N four times. The spring

shows extensions of 0.23m, 0.25m, 0.25m and 0.24m. Calculate the spring constant for this spring

3. For the spring in the question above, calculate the force when the extension of the spring is 100cm.

4. A second spring is loaded with 100N. It shows an extension of 60cm. What is the difference between the spring constants of the two springs?

5. What would be the force required to extend the second spring by 0.45m?


What is work?LO: understand how energy can be transferred

An object is said to have done WORK when it transfers (uses) energy

Calculating workLO: understand how energy can be transferred

The work done by an object is equal to the amount of energy that it transfers

Work done = force x distanceW = f x d

• W = work done(J)• f = force (N)• d = distance(m)

Example 1An object of weight 40N is raised by a height of 0.4m. Calculate the work done in raising the object.

LO: understand how energy can be transferred

Example 22000J of energy is transferred by a sprinter as he runs a distance of 100m. Calculate the force that is exerted by the sprinter as he is running.


Example Questions1. What is the definition of work done?2. What is the unit for energy?3. The engine of a car exerts a force of 750N. How much energy

would be transferred by the engine if the car moved a distance of 100m?

4. An object of weight 50N is raised by a height of 200cm. What is the work done in raising the object?

5. 700J of energy is used by a person to move a distance of 10m. What is the force exerted by the person as they walk the distance?

6. Object A has a weight of 200N. Object B has a weight of 350N. If 1000J of energy is used to raise each object, which object will gain the most height?


Calculating powerLO: understand how energy can be transferred

Power is the amount of work done/energy transferred in a given time

Power = work done / timeP = W / t

• P = power (W)• W = work done (J)• t = time (s)

Example 1An object of weight 700N is raised by a height of 2m in a time of four seconds. Calculate the work done in raising the object and the power.


Example Questions1. A car engine transfers 3000J in 20 seconds. What is the

power generated by the engine?2. 400J of energy is transferred in raising an object in 1

minute. What is the power?3. A kettle has a power rating of 2000W. How much work is

done by the kettle in boiling water in 40 seconds?4. A student of weight 500N transfers 2000J whilst running

up some stairs. She reaches the top of the stairs in 3 seconds. How high are the stairs and what is her power?

5. A sprinter can generate 150W whilst running. If he transfers 450J of energy, how long has he been running for?


Gravitational Potential Energy

Any object that is raised above the ground will

have gravitational potential energy

LO: understand the nature of gravitational potential energy

Gravitational Potential Energy

GPE = mass x


GravitationalField strength x height

GPE = m x g x h

• GPE = gravitational potential energy (J)

• m = mass (kg)• g = gravitational field strength

(N/kg)• h = height (m)

Example 1An object of mass 10kg is raised by a height of 20m. What is the gravitational potential energy of the object?


Example 2An object gains gravitational potential energy of 300J. If the mass of the object is 3kg, what is the height that the object has been raised?


Kinetic energy

All objects that are moving have kinetic

energy!

LO: understand the nature of kinetic energy

Kinetic energy

KE = ½ x m x v²


• KE = kinetic energy (J)• m = mass (kg)• v = velocity (m/s)

Example 1An object has a mass of 2kg and is moving with a velocity of 5m/s. What is the kinetic energy of the object?


Example 2An object of mass 300g has 600J of kinetic energy. How fast is the object moving?


Example questions1. What is the equation that is used to calculate the kinetic

energy of an object?2. Calculate the kinetic energy of an object of mass 500g

that is moving with a velocity of 20m/s3. A car of mass 500kg is a moving with a velocity of 10m/s.

It accelerates to a velocity of 15m/s. What is the KE of the object before and after it accelerates?

4. A sprinter has kinetic energy of 1000J and a mass of 68kg. How fast is the sprinter running?

5. A ball of mass of 0.5kg is dropped from a height of 2m. Assuming that all of the GPE is transferred to KE, what will be the velocity of the ball when it hits the ground?


Momentum

ALL MOVING OBJECTS HAVE MOMENTUM!

LO: understand what is meant by momentum

Momentum

P = m x v


• P = momentum (kgm/s)• m = mass (kg)• v = velocity (m/s)

Example question 1An object of mass 300g is moving with velocity of 5m/s. What is its momentum?


Example question 2An object has momentum of 50kgm/s. If the object has a mass of 25kg, what is its velocity?


Example questions1. What is the momentum of a bullet of mass 50g travelling at

300 m/s?2. What is the momentum of a dog (mass 12 kg) fired out of a

canon at 120 m/s?3. Calculate the momentum of a 65 kg sprinter when

travelling at 9.5 ms-1.4. Calculate the velocity of a car of mass 700 kg that has the

same momentum as the sprinter in Q35. A body has a mass of 2.5 kg. Calculate:• Its momentum when it has a velocity of 3.0 m/s• Its velocity when it has a momentum of 10.0 kgm/s


Conservation of momentum

In a closed system, the total momentum before an event and the total momentum after an event are the same. This is called conservation of momentum.

Events you may be asked about in your exams are:• Collisions• Explosions


Example 1A railway engine of mass 800kg travelling at 5m/s collides with and becomes attached to a truck of mass 200kg travelling at 2m/s. Calculate the speed of the truck and engine after the collision


Example 2A 0.5kg trolley is pushed at a velocity of 1.2m/s into a stationary trolley of mass 1.5kg. The two trolleys stick to each other after the impact. Calculate:• The momentum of the 0.5kg trolley before the collision• The velocity of the two trolleys straight after the impact


Brakes and crumple zonesBrakes and crumple zones are two of the main safety

features on a car

LO: explain how safety features on a car work

Brakes and crumple zonesBoth features work by transferring kinetic energy into other

forms. What energy transfers take place in each of these features?

LO: explain how safety features on a car work

Structure of an atomLO: understand static electricity

All matter is made up of atoms

However, an atoms is NOT the smallest unit of matter like you might have been

previously taught

Atoms of themselves made of smaller particles

What is an atom made up of?LO: understand static electricity

Protons – Positively charged particles found inside the

nucleus

Neutrons – Neutral particles found inside the nucleus

Electrons – Negatively charged particles that orbit

the nucleus

Static electricity by frictionLO: understand static electricity

When you rub one of the rods with the cloths, you create static electricity. This happens in one of two ways.

For the polythene rod, the dry cloth transfers electrons TO the surface of the rod and gives it a negative charge

Static electricity by frictionLO: understand static electricity

When you rub one of the rods with the cloths, you create static electricity. This happens in one of two ways.

For the perspex rod, the dry cloth transfers electrons away from the surface of the rod. This gives it a positive charge

Static electricity rulesLO: understand static electricity

1. Like (The same) charges attract2. Unlike (The opposite) charges repel

Key definitions

When considering electricity, we will usually use three key terms:

1) Current: This is the flow of electric charges around a circuit. The size of the current is dependent on the rate of flow of electric charges

2) Potential Difference (Voltage): The potential difference between two points is the work done per unit charge between two points

3) Resistance: This is the resistance to the flow of electrons around a circuit

LO: Understand how to create electrical circuits

Calculating current

I = Q/t


• I = Current (Amps, A)• Q = Charge (Coulombs, c)• t = Time (s)

Example question 1Calculate the current when 4C passes a point in 8 seconds


Example question 2An ammeter is records a current of 8A. Calculate how much charge is passing through the ammeter in 10 seconds.


Task1. What is the current when 20C of charge pass through an

ammeter in 2minutes?2. A battery can produce 20A of current. How much charge

does it discharge in 30s?3. Another battery can produce a charge of 30A. How long

will this battery be running before it has discharge the same amount of charge as the battery in Q2?

4. A car engine requires a battery that can produce a current of 40A to start. A mechanic places a battery that can discharge 100C in 30s into a car. Will this battery be good enough to start the car? Why?

5. For the question above, how much charge would the battery have to discharge in 30s to start the engine?


Calculating voltage

V = W/Q


• V = Voltage (Volts, V)• W = Work done (Joules, J)• Q = Charge (Coulombs, c)

Example question 1A battery transfers 30J for every coulomb of charge that passes through the battery. What is the potential difference of the battery?


Example question 2A battery has a voltage rating of 40V. How much energy is transferred by the battery if 20C of charge pass through the battery?


Task1. What is the voltage of a battery if it transfers 40J of

energy for every 10C that pass through it?2. A builder requires a 400V battery to power his

pneumatic drill. He is told that a battery transfers 1000J for every 3C of charge that pass through it. Will this battery be good enough? Why?

3. How much energy would the battery in the question above need to transfer for every 3C to have a voltage of 400V?

4. Battery A has a rating of 300V. Battery B has a rating of 500V. What is the difference in the amount of work done by the two batteries if 20C of charge pass through both batteries?


Circuit symbolsLO: Understand how to create electrical circuits

Ohm’s Law

Ohm’s Law states that the current through a resistor is proportional to the potential difference provided the temperature is constant

LO: Understand the relationship-between current and voltage in a circuit

Ohm’s Law

V = IR


• V = Voltage (V)• I = Current (A)• R = Resistance

(Ohms, Ω)

Ohm’s Law 1Calculate the potential difference across a 4Ω resistor when the current through it is 10A.


Ohm’s Law 2The potential difference across a 30Ω is 20V. What is the current through the resistor?


TaskCalculate:1. The resistance of a bulb if the current is 0.5 A and the

potential difference across the bulb is 2 V.2. The potential difference across a bulb if the resistance

of the bulb is 3 and the current flowing is 2 A3. The potential difference across a resistor of 5 with a

current of 1.5 A.4. The total resistance of a circuit if the potential

difference across the cell is 12V and the current is 3 A.5. The current flowing in a circuit with a total resistance

of 5 and a potential difference across the cell of 6V.


Non-Ohmic Components1

An LED does not follow Ohm’s law and is

designed to only allow current to flow through in

one direction



An LED does not follow Ohm’s law and will only light up when current to

flows through in the right direction.

If current tries to flow in the other direction it

encounters a MAHOOSIVE resistance!



An LDR is a component whose resistance

decreases as the light intensity that falls on it

increases

Where would this be useful?



A thermistor is a component whose resistance decreases when the temperature increases.

Where would this be useful?


AC vs DC

If you turn on any battery powered device the electricity will only ever flow in one direction.

This is called DIRECT CURRRENT (d.c.) as the electricity goes around in just one direction.

LO: describe features of mains electricity

AC vs DC

However, the same isn’t true for mains electricity. Mains electricity uses ALTERNATING CURRENT (a.c.) which repeatedly flows in one direction and then reverses its flow. The frequency is how many times it changes direction in one second


Key points

1. Mains electricity uses a.c.

2. Mains electricity is at 230V

3. Mains electricity has a frequency of 50Hz. This means it changes direction 50 times in one second


Cables and Plugs

Cables and wires are designed to allow people to

use them without risk of hurting themselves. Most

appliances are supplied with three-core cable. This means the cable is made up of three

separate wires.


Components of a plug and cable1) Live wire (brown) – This

carries the current to the appliance. Touching this can be deadly!

2) Neutral wire (blue) – This completes the circuit and is usually at 0V

3) Earth wire (green/yellow) – This ‘earths’ the appliance in case one of the wires touches the casing

4) Fuse – This stops the flow of current if it gets too high


Earthing

Components are earthed to make sure you don’t get an electric shock if the live wire accidentally touches the casing. The electricity will flow harmlessly through the earth wire instead of through you when you touch the casing.

However, appliances with plastic cases (hairdryers etc.) don’t have earth wires. Why is this?


Earthing

Plastic is an insulator, so there is no danger if the live wire touches

the casing. Therefore, these appliances are supplied with two-core cables instead of three-core cables i.e. they don’t have earth wires because they don’t need

them


Fuses

A fuse is a component that has a wire running through

it made of a different material/thickness than the

rest of the circuit. It is designed to stop current that is too high flowing

through it.


FusesFuses have a rating based on the amount of current they will allow through. For example, a 13A fuse will allow a maximum of 13 amps

of current to flow through. If MORE than this tries to flow

through, the wire heats up and melts, breaking the circuit and

protecting the appliance


Advantages/Disadvantages?

Circuit BreakersCircuit breakers are fitted in

newer homes. They measure the difference in current in the live

and neutral wires. If the difference is too great, an

electromagnetic switch opens (‘trips’) which stops the flow of current. They work a lot faster

than fuses and can be reset easily


Advantages/Disadvantages?

Circuit Breakers

Use the textbook spread to create a poster on fuses and circuit breakers. Your poster to include details of how they

work and advantages and disadvantages of both


Knowledge checkCopy the true sentences and change the false sentences to make them true:1. The earth wire in a three-core cable is usually brown2. Appliances with metal casings are supplied with three-

core cables3. Fuses stop current flowing through a circuit by melting

when the current flowing through them is above a certain value

4. A circuit breaker works by monitoring the difference in current between the live and earth wire

5. Mains electricity uses direct current at 100Hz.


QWC PracticeUsing as much detail as possible, explain how fuses and circuit breakers work to protect people and appliances.

Which, in your opinion, is the better choice for installation into a home and why?

5-6 marks criteria:• Knowledge of accurate information appropriately contextualised• Detailed understanding, supported by relevant evidence and

examples• Answer is coherent and in an organised, logical sequence,

containing a wide range of appropriate or relevant specialist terms used accurately

• The answer shows almost faultless spelling, punctuation and grammar.


Calculating powerLO: describe features of mains electricity

P = V x I

• P = Power (w)• V = Voltage (V)• I = Current (A)

Example 1Calculate the power of a bulb if it is supplied with a potential difference of 230V and the current flowing through it is 0.4A


Example 2A kettle has a power rating of 1000W. If it is supplied with a potential difference of 230V, what is the current flowing through it?


Example questions1. A light bulb is connected to a 2V supply and experiences a

current of 6.4A. What is the power rating of the bulb?2. A kettle has a power rating of 1500w. What is the potential

difference that it must be supplied with to have a current flowing through it of 30A?

3. A student attaches a 10V supply to a bulb with a power rating of 100w. What is the current running through the bulb?

4. The student now connect a 25w bulb to the same supply. What is the difference between the current going through this bulb compared to the 100w bulb?

5. Bulb A transfers 1000J in 10seconds. Bulb B transfers 1500J in 3 seconds. Which bulb will have a higher current running through it when connected to a 12V supply?


Calculating energy

E = V x Q


• E = Energy transferred (Joules, J)• V = Voltage (Volts, V)• Q = Charge (Coulombs, c)

Example question 1A battery transfers 30J for every coulomb of charge that passes through the battery. What is the potential difference of the battery?


Example question 2A battery has a voltage rating of 40V. How much energy is transferred by the battery if 20C of charge pass through the battery?


Task1. What is the voltage of a battery if it transfers 40J of

energy for every 10C that pass through it?2. A builder requires a 400V battery to power his

pneumatic drill. He is told that a battery transfers 1000J for every 3C of charge that pass through it. Will this battery be good enough? Why?

3. How much energy would the battery in the question above need to transfer for every 3C to have a voltage of 400V?

4. Battery A has a rating of 300V. Battery B has a rating of 500V. What is the difference in the amount of work done by the two batteries if 20C of charge pass through both batteries?


What is an atom made up of?

Protons – Positively charged particles found inside the

nucleus

Neutrons – Neutral particles found inside the nucleus

Electrons – Negatively charged particles that orbit

the nucleus

LO: understand the nature of radioactive decay

Protons, neutrons and electrons

Particle Relative charge Relative massProton +1 1Neutron 0 1Electron -1 1/2000

Where is the majorityof the mass of the atom?


Relative sizesLO: understand the nature of radioactive decay

Atomic and Mass numberAtomic number: This is the number of protons inside the

nucleus of an atom

WARNING: Even though the number of protons and electrons in a neutral atom are the same, make sure you say the correct definitions if you are asked in an exam!

Mass number: This is the number of protons + neutrons in the nucleus of an atom


Atomic and Mass numberAtomic number: This is the number of protons inside the

nucleus of an atom

Mass number: This is the number of protons + neutrons in the nucleus of an atom

Which is which?


Example 1Calculate the following quantities for the element below(i) Atomic number(ii) Mass number(iii) Number of protons(iv) Number of electrons(v) Number of neutrons


Example 2Calculate the following quantities for the element below(i) Atomic number(ii) Mass number(iii) Number of protons


TaskUse your periodic table to find the following quantities for: nitrogen, oxygen, iron, platinum, gold, lead, mercury, potassium, calcium, phosphorus, argon, xenon(i) Atomic number(ii) Mass number(iii) Number of protons(iv) Number of electrons(v) Number of neutrons

If the numbers are decimals, round them to the nearest whole number


The Plum Pudding Model - 1897LO: understand the nature of radioactive decay

Enter RutherfordLO: understand the nature of radioactive decay

Ernest Rutherford fired alpha particles at gold foil. Alpha particles have a positive charge and he expected them to go through the particle, with a small amount of deviation from their path

Gold Foil Experiment - 1911LO: understand the nature of radioactive decay

The results are very different!

Most alpha particles go straight through with no deviation! Some, however, are diverted through very large angles! The physics community is flummoxed by this finding!

ConclusionsLO: understand the nature of radioactive decay

Most of the fast, highly charged alpha particles went whizzing straight through undeflected.

SUGGESTS THAT MOST OF THE ATOM IS EMPTY SPACE!!


Some of the alpha particles were deflected back through large angles.

A very small number of alpha particles were deflected backwards!

SUGGESTS THAT THERE IS A CONCENTRATED POSITIVE MASS

SOMEWHERE IN THE ATOM.


A very small number of alpha particles were deflected backwards!

SUGGESTS THAT THE CONCENTRATED MASS IS MINISCULE COMPARED TO

THE SIZE OF THE REST OF THE ATOM, BUT CONTAINS MOST OF THE MASS

Types of RadiationLO: understand the nature of radioactive decay

There are three different kinds of radiation. Each one has a unique nature and penetration

Alpha radiation:

This particle is made up of two protons and two neutrons (i.e. a Helium nucleus). It has a charge of +2 and moves slowly because of it’s large mass. It can be stopped by a few cm of air or by a piece of paper



Beta radiation:

During beta radiation, a neutron turns into a proton inside the nucleus and gives off an electron, which is fired from the nucleus. The electron is small and light and so moves very fast! Beta particles can be stopped by a thin sheet of aluminium



Gamma radiation:Gamma radiation usually follows alpha or beta decay. It is NOT a particle like the other two. It is a high energy EM wave that travels at the speed of light (the fastest that anything can travel Joel). It can only be stopped by a very thick piece of lead or concrete.

IsotopesLO: understand the nature of fusion and fission

The diagram below shows three isotopes of hydrogen. What is the same and different for each

isotope of hydrogen?

IsotopesLO: understand the nature of fusion and fission

An isotope of an element has the same number of protons and neutrons as the original, but a

different number of neutrons.

Radioactivity of a substanceLO: understand the nature of fusion and fission

Radioactivity of a substanceLO: understand the nature of fusion and fission

As a radioactive substance decays, the number of particles left in it will start to reduce. Therefore the radioactivity of the substance will begin to decrease. It will continue to decrease, until the radioactivity has reached zero!

Half-lifeLO: understand the nature of fusion and fission

The half-life of a substance is the time it takes for HALF of the particles in a sample to decay or for the radioactivity of a substance to decrease by HALF.

Half-lifeLO: understand the nature of fusion and fission

What is the half life of this substance?

RecapLO: understand the nature of fusion and fission

In each atom, the number of protons will ALWAYS be the same as the number of electrons. This makes sure that the overall charge is zero.

Particle Charge

Proton +1

Neutron 0

Electron -1

http://www.google.co.uk/url?sa=i&source=images&cd=&cad=rja&docid=YEXIWMm26FeI_M&tbnid=tlbjR2Iqbdpb4M:&ved=0CAgQjRwwAA&url=http://www.realnewsreporter.com/?p=1720&ei=oYusUfo5zpKGB4PCgcAI&psig=AFQjCNH3OHPhzGbDVzQ6aibr5NTcwAYPAQ&ust=1370348833053298

Nuclear FissionLO: understand the nature of fusion and fission

Nuclear fission is a process that uses atoms to generate VAST amounts of

energy.

HOW DOES IT WORK?

Uranium nucleus

Neutron


To begin with, we have a simple Uranium nucleus.

Uranium is used because it is already unstable.

A slow moving neutron is fired at the Uranium.

Uranium nucleus

Neutron


The neutron attaches itself

to the uranium and makes it even more unstable!

Unstable nucleus

Uranium nucleus

Neutron


The unstable Uranium splits into two smaller nuclei,

releasing energy in the process

Unstable nucleus

2 smaller nuclei (e.g. barium and

krypton)

Uranium nucleus

Neutron


Along with the energy, some more neutrons are also

released!

Unstable nucleus


krypton)

More neutrons

Chain reactionsLO: understand the nature of fusion and fission

More neutrons

These fission reactions produce a lot of energy and are used in

nuclear generators.

However, each fission reaction produces more and more neutrons.

WHY MIGHTTHIS BE BAD?

Chain reactionsLO: understand the nature of fusion and fission

More neutrons

Each of the neutrons can cause more fission reactions, releasing more energy and more neutrons. The reaction can soon become an

uncontrollable chain reaction,and when that happens…

http://www.google.co.uk/url?sa=i&source=images&cd=&cad=rja&docid=YEXIWMm26FeI_M&tbnid=tlbjR2Iqbdpb4M:&ved=0CAgQjRwwAA&url=http://www.realnewsreporter.com/?p=1720&ei=oYusUfo5zpKGB4PCgcAI&psig=AFQjCNH3OHPhzGbDVzQ6aibr5NTcwAYPAQ&ust=1370348833053298

Using fissionLO: understand the nature of fusion and fission

http://www.google.co.uk/url?sa=i&source=images&cd=&cad=rja&docid=-xqYhokg_3YUyM&tbnid=Xi1jel0L0-qytM:&ved=0CAgQjRwwAA&url=http://myweb.rollins.edu/jsiry/Fission.html&ei=ppOsUaq-CMyThQfwo4D4Cg&psig=AFQjCNEN-aofyFAYkdwK3RD9hWyOujSKrQ&ust=1370350886185480

True or False?LO: understand the nature of fusion and fission

Copy the true sentences and change the false sentences to make them true1) Nuclear fission uses fast-moving electrons2) The most common fuel used in a nuclear reactor is uranium3) Nuclear fission involves one nucleus splitting into smaller

nuclei and releasing energy in the process 4) An advantage of nuclear fission is that it doesn’t produce

any harmful radioactive waste5) A chain reaction occurs when too many neutrons cause

fission reactions and the process can no longer be controlled

Nuclear fusion

http://www.google.co.uk/url?sa=i&source=images&cd=&cad=rja&docid=pzAsxonZUE1TYM&tbnid=L3XLz_mmIOs89M:&ved=0CAgQjRwwAA&url=http://people.bath.ac.uk/ssk21/Nuclear%20fusion%20and%20the%20tokamak.html&ei=AZ2sUeDHKMinhAf0hoHgAw&psig=AFQjCNFcTrOWI-PPktw6Y7CUi0fwo2VjEg&ust=1370353281706913

Nuclear fusionLO: understand the nature of fusion and fission

Although the names sound very similar, fission and fusion are VERY DIFFERENT

PROCESSES.

Uranium nucleus

Neutron


In fission, one nuclei is split into smaller nuclei to release

energy!

Unstable nucleus


krypton)

More neutrons

Nuclear fusionLO: understand the nature of fusion and fission

In nuclear fusion, two nuclei are fused together to release energy. It is the

opposite of nuclear fission.

Where does this happen?LO: understand the nature of fusion and fission

Contrary to popular belief, our sun is not a

massive fireball. It is actually a

massive fusion reactor!


Where does this happen?LO: understand the nature of fusion and fission

The sun is made up of mainly hydrogen. The high temperature on

the sun allows the hydrogen to fuse

together and make helium, releasing

massive amounts of energy in the process

Why don’t we use fusion?LO: understand the nature of fusion and fission

Fusion seems like a great process! We

only need hydrogen to do it (which we can get from water) and

make helium, which is not a greenhouse

gas…so why are we not using it?


Fusion futureLO: understand the nature of fusion and fission

Although fusion isn’t economically viable

right now, it will (probably!) be one of

the main ways we generate energy in the future. Lots and lots of

research is currently being done into it

currently….


NebulaLO: understand the lifecycle of a star

All stars start their lives as part of a nebula. Nebulae

are large clouds of dust and gas

(mainly hydrogen).

http://www.google.co.uk/url?sa=i&source=images&cd=&cad=rja&docid=I6l6Oh4KFClSsM&tbnid=9DEzmbXpsbbC9M:&ved=0CAgQjRwwAA&url=http://en.wikipedia.org/wiki/File:Crab_Nebula.jpg&ei=xaWsUbOZLYSxhAe1sYGQCg&psig=AFQjCNGxABfexcdpanuwenZZmZ602yA07g&ust=1370355525821184

ProtostarLO: understand the lifecycle of a star

Over millions of years, gravity will cause the dust and gas in the nebula to

come together. As it does this, the temperature

increases until hydrogen can fuse. When this happens, a

protostar is born. This is kind of like a ‘baby’ star.

http://www.google.co.uk/url?sa=i&source=images&cd=&cad=rja&docid=j6l0C8yV_5_JqM&tbnid=s7iZdNiUbsGdmM:&ved=0CAgQjRwwAA&url=http://commons.wikimedia.org/wiki/File:Protostar_Herbig-Haro_46_47.jpg&ei=SqasUYTvGomThgeJw4DADg&psig=AFQjCNHTHH0TKkGk0TRsIX9oDALuEWsXGg&ust=1370355658484097

Main sequence starLO: understand the lifecycle of a star

The main sequence star is the next stage after a

protostar. Hydrogen fusion is now in full flow and the

star is much hotter and brighter than the protostar.

http://www.google.co.uk/url?sa=i&source=images&cd=&cad=rja&docid=1q3g6V-CipziWM&tbnid=XvECOK02ollSpM:&ved=0CAgQjRwwAA&url=http://library.thinkquest.org/05aug/00108/mainsequence_frameset.htm&ei=AqesUfTRKYfLhAfJ3ICQCg&psig=AFQjCNGcrhfO79lscvh2ZDEF82RjWK4opQ&ust=1370355842725935

Red Giant starLO: understand the lifecycle of a star

When a star runs out of hydrogen, it begins to fuse other, heavier elements.

This releases more energy, causing the star to expand.

It also gives off red light, giving it the name ‘Red

Giant’.

http://www.google.co.uk/url?sa=i&source=images&cd=&cad=rja&docid=sijxciKA4q6CdM&tbnid=tkoXg3yQSzKXaM:&ved=0CAgQjRwwAA&url=http://throughmyspecs.co.uk/2012/06/04/stars/&ei=uKisUYr1F4iJhQfwsYCABA&psig=AFQjCNGUAQKb5QKDEnToQuVGSvm01GuGkg&ust=1370356280433458

White dwarfLO: understand the lifecycle of a star

When the red giant has run out of all fuel and can fuse

nothing more, it will lose its outer layers. This leaves just

the core, which is still extremely hot. It is so hot it glows white hot, giving the

name to this stage – the ‘white dwarf’.

http://www.google.co.uk/url?sa=i&source=images&cd=&cad=rja&docid=ki1SApu-HLJGIM&tbnid=3K0i9L0pJiZkVM:&ved=0CAgQjRwwAA&url=http://www.dailygalaxy.com/my_weblog/2013/02/-white-dwarf-stars-offer-best-potential-to-identify-habitable-planets.html&ei=gqmsUeO2M4SThQffEQ&psig=AFQjCNEpNsQOSQDnJUqvb1XuITsIAfspbQ&ust=1370356482894584

Black dwarfLO: understand the lifecycle of a star

After a long enough time, the white dwarf will cool down enough so that it

stops glowing white hot. It is now called a ‘black

dwarf’.

http://www.google.co.uk/url?sa=i&source=images&cd=&cad=rja&docid=X86JWB_VumRyJM&tbnid=MpJC7mz4C7UWMM:&ved=0CAgQjRwwAA&url=http://www.clipart.dk.co.uk/1341/subject/Physics/Black_dwarf&ei=C6qsUcP5PMXChAfi5YDQCg&psig=AFQjCNHxHAorrcQLyrG9i0hu6xsPPSDQzg&ust=1370356620039996

TaskLO: understand the lifecycle of a star

The lifecycle that you have just covered is for

stars about the same mass as our

sun…Heavier stars, however, lead a slightly different life

Red Super Giant starLO: understand the lifecycle of a star

Following the main sequence, the star begins to

fuse together heavier elements. However, as it

has far more fuel, it expands to a much larger size and gives off much

more energy.


SupernovaLO: understand the lifecycle of a star

For very heavy stars, once they have run out of fuel, the star begins to collapse in on itself. It continues to collapse until it reaches a critical point when it can’t

collapse any more. This causes a MASSIVE

shockwave!

http://www.google.co.uk/url?sa=i&source=images&cd=&cad=rja&docid=J7aXulTvdQeQ5M&tbnid=xS6kjpTuMYLFzM:&ved=0CAgQjRwwAA&url=http://www.mpa-garching.mpg.de/mpa/institute/news_archives/news1005_janka/news1005_janka-en.html&ei=Kq2sUeCoLo6IhQeP5oGwDA&psig=AFQjCNF8WUa_WUUT-KwOq2b0CTJS7_e6Rw&ust=1370357418808685


The shockwave is so large that the outer layers

EXPLODE outwards! The explosion only lasts

seconds, but can release as much energy in those

seconds as the star has released up to that point! It can be as bright as the light

from 10billion stars.

http://www.google.co.uk/url?sa=i&source=images&cd=&cad=rja&docid=J7aXulTvdQeQ5M&tbnid=xS6kjpTuMYLFzM:&ved=0CAgQjRwwAA&url=http://www.mpa-garching.mpg.de/mpa/institute/news_archives/news1005_janka/news1005_janka-en.html&ei=Kq2sUeCoLo6IhQeP5oGwDA&psig=AFQjCNF8WUa_WUUT-KwOq2b0CTJS7_e6Rw&ust=1370357418808685

Neutron starLO: understand the lifecycle of a star

After a supernova, only the star’s core is left behind.

During the collapsing process, this core is turned

into just neutrons.

The resulting ‘neutron star’ is very very dense. One

spoonful of a neutron star would weigh more than the

Earth!

http://www.google.co.uk/url?sa=i&source=images&cd=&cad=rja&docid=Fue8CAxWIeKGWM&tbnid=iIyioqsmDX6NdM:&ved=0CAgQjRwwAA&url=http://commons.wikimedia.org/wiki/File:Neutron_star_illustrated.jpg&ei=866sUYO9JcLLhAe7oIGoBg&psig=AFQjCNFHQ6p2zZQbwrtoQefpk06Gq_rXOA&ust=1370357875661966

Black holeLO: understand the lifecycle of a star

In some very very rare cases, the core of a star left over after a supernova will continue to collapse. It will

keep getting smaller and smaller until the whole star

has collapsed into an infinitely small point.

http://www.google.co.uk/url?sa=i&source=images&cd=&cad=rja&docid=qm990fvoSNBlhM&tbnid=G95JJwKowFCRAM:&ved=&url=http://spore.wikia.com/wiki/Black_hole&ei=IrWsUZG5L8aThgez-4G4Bw&psig=AFQjCNHIm5Im4ElEiDD_5HxYFeQzBgUjig&ust=1370359458837492

Black holeLO: understand the lifecycle of a star

This ‘singularity’ has an immense gravitational

force. It’s attraction is so strong that not even light can escape from it. Hence

the name ‘black hole’.

http://www.google.co.uk/url?sa=i&source=images&cd=&cad=rja&docid=qm990fvoSNBlhM&tbnid=G95JJwKowFCRAM:&ved=&url=http://spore.wikia.com/wiki/Black_hole&ei=IrWsUZG5L8aThgez-4G4Bw&psig=AFQjCNHIm5Im4ElEiDD_5HxYFeQzBgUjig&ust=1370359458837492

How elements are formedLO: understand the lifecycle of a star

Stars are the perfect place for elements to be made! They are like massive ovens that have the energy needed to make new elements


Stage 1LO: understand the lifecycle of a star

When a star is ‘young’ it has plenty of hydrogen. It fuses the hydrogen together to form helium. This releases massive amounts of energy in the form of light and heat.

But what happens when the hydrogen runs out?



When a star runs out of hydrogen, it has massive amounts of helium left. It has no choice but to start fusing helium, instead of hydrogen.

Fusing helium makes heavier elements, like lithium and beryllium.



Fusing helium releases more energy than fusing hydrogen. This makes the star bigger and it enters the red giant phase.

But what does it do when it runs out of helium?



When the star has run out of helium, it will start fusing the heavier elements that it has created. This will make even heavier elements, such as Boron and Carbon.



The star will keep on going through this process of running out of fuel and fusing heavy elements that it has created. This will make heavier and heavier elements.

The heaviest element that stars can make is Iron.


What about elements heavier than Iron?

LO: understand the lifecycle of a star

http://www.google.co.uk/url?sa=i&source=images&cd=&cad=rja&docid=dci0TGZmnhQ49M&tbnid=iLUezgxlSffS6M:&ved=0CAgQjRwwAA&url=http://www.chemicool.com/&ei=f7q5UeqFIIqYhQfG1oGIAQ&psig=AFQjCNGBz2gUz7A6Kbc9uqEeN4tVenvEtw&ust=1371212799591220


The temperature in stars is not hot enough to make elements heavier than Iron. For these temperatures, a supernova is required!

http://www.google.co.uk/url?sa=i&source=images&cd=&cad=rja&docid=Fev-pOCDgbGLfM&tbnid=7N_6OWMKtEHArM:&ved=0CAgQjRwwAA&url=http://en.wikipedia.org/wiki/File:Keplers_supernova.jpg&ei=Sru5UeC5C9GO7Qaa24G4Cg&psig=AFQjCNHjqjb3yB9ozQDonmtYgOteySJoPQ&ust=1371213002311379

p2 forces between objects when two objects push or pull on each other, they exert equal and opposite...

Documents

force slide

force n

effects of forces

opposite forces

vertical resultant forces

multiple forces

driving force

single force